docs: def create_key_file(service, key):
      """Create a file containing key."""
      keyfile = _keyfile_path(service)
      if os.path.exists(keyfile):
          log('Keyfile exists at %s.' % keyfile, level=WARNING)
          return
  
      with open(keyfile, 'w') as fd:
          fd.write(key)
  
      log('Created new keyfile at %s.' % keyfile, level=INFO)